Breastpumps for use by nursing mothers are well known. They allow the nursing woman to express the breastmilk as necessary or convenient, and further provide collection of the breastmilk for later use. For some mothers, breastpumps may be a necessity, such as when the child has suckling problems, or if the mother has problems with excessive or deficient milk production, or soreness, deformation or injury of the mammilla.
Manual breastpumps are commonplace, primarily because they are relatively inexpensive and easy to transport. Being manually driven, however, stroke rate and suction pressure produced can be uneven. Use of a manual pump also may require two hands: one to hold the pump in place, the other to manipulate the piston pump or squeezebulb.
Electrically-driven breastpumps are also commonplace. They may be of a substantially large size of a non-portable or semi-portable type, typically including a vacuum pump which has a substantial electric motor that plugs into standard house current. Advantages of this type of pump are ready controllability and regulation of the vacuum, and the ability to pump both breasts at once. That is, the nursing woman has both hands free to hold two breastpump shields in place for pumping of both breasts at the same time.
Battery-driven breastpumps have also been developed. These breastpumps have the advantages of controllability and regulation of the vacuum, as well as being easily carried. Such a battery-driven portable breastpump is described in U.S. Pat. No. 4,964,851, for example. This breastpump, sold under the name MINIELECTRIC by Medela, Inc., is lightweight and achieves good vacuum (i.e., negative pressure) regulation in preferred limits, for example, between 100 and 220 mmHg.
Applicants are not aware, however, of any small hand-held motor-driven breastpump, such as battery-powered, which has been developed for double-breast pumping. Applicants also are not aware of any prior art breastpump which alternates a suction stroke (pull) on two breasts in a double-pumping mode; those breastpumps known to Applicants apply vacuum simultaneously to both of the breasts. It is known, however, to alternate a compression (increased pressure) stroke between two breasts being pumped, but with a continuous vacuum to the breasts, as shown in U.S. Pat. No. 4,607,596.